This was a case of good intentions but bad execution. Heng's goal was to protect his former girl friend from domestic abuse. The problem was that even the most recent incident was several hours in the past. At the time of the fatal encounter, Lane was simply returning to his apartment. Because the girl friend wasn't in imminent danger, Heng had no right to interfere with him. If anything, Lane was defending himself against Heng. Had Heng overheard Lane beating the girl friend, he would have been justified in kicking in the door and shooting Lane if that's what it took.
Whenever there is a significant possibility that a confrontation could turn violent, it's best to get the police involved as early as possible. Since we are all good guys here, we have nothing that we wouldn't want them to witness. If the bad guy won't behave himself, let him fight the police rather than us. It's their job and, more importantly, they have better legal cover than we do.
I follow a self defense blog written by an Ohio police officer named Greg Ellifritz. I e-mailed him the following question: What would be the response if a woman called 911 and told them, "I just broke up with my boy friend and want to move my stuff out of his place. He has a bad temper and I'm afraid of what he will do if he finds me there. Can you send an officer to watch over me?" Ellifritz's reply was that this is a frequent request that they are more than willing to oblige.
Over the past year, three domestic abuse situations in Omaha have gone bad when friends or relatives of the victim tried to help. An abusive husband was shot to death when he attacked the wife's friend. Two brothers were shot to death when their sister's abuser discovered them helping her move out. The abuser committed suicide after a standoff. The Heng/Lane incident is the third. Each one could have been avoided by getting the police involved at the beginning. They might still have ended with the abuser dead but the helpful friends and relatives would have been spared their grief.